Grinding machine

ABSTRACT

A grinding machine making use of a conical abrasive wheel wherein provision is made for performing a rough grind with the large end of the wheel and a finish grind with the small end of the wheel, a gage being inserted into the workpiece during the finish grind only.

United States Patent [191 Uhtenwoldt et al.

[ GRINDING MACHINE [75] Inventors: Herbert Rudolf Uhtenwoldt,

Worcester; Robert Gordon l-latstat, Rutland, both of Mass.

[73] Assignee: Cincinnati Milacron-Heald Corporation, Worcester, Mass.

22 Filed: Mar. 30, 1972 21 Appl. No.: 239,559

[52] US. Cl. 5l/l65.91, 51/165931 [51] Int. Cl B24b 49/04 [58] Field of Search 51/165 R, 165.91,

[56] References Cited UNITED STATES PATENTS 2,139,896 12/1938 Johnson 51/l65.93 X

[111 3,774,349 [4 1 Nov. 27, 1973 6/1950 Arms et al. 51/165.93 X 12/1964 Lockwood et a1. 51/165.91 X

Primary ExaminerHarold D. Whitehead AttorneyNorman S. Blodgett [57 ABSTRACT A grinding machine making use of a conical abrasive wheel wherein provision is made for performing a rough grind with the large end of the wheel and a finish grind with the small end of the wheel, a gage being inserted into the workpiece during the finish grind only.

7 Claims, 10 Drawing Figures Patented Nov. 27, 1973 3,774,349

8 Sheets-Sheet 1 Patented Nov. 27, 1973 3,774,349

8 Sheets-Sheet v FIG. 3

Patented Nov. 27, 1973 3,774,349

8 Sheets-Sheet 3 Patented Nov. 27, 1973 3,774,349

8 Sheets-Sheet 4 FIG. 5

4 TABLE IN I (DRESS) TABLE INDEx IN/J TABLE/N SPEED DRES$ER DOWN RETRAcTIoN FRONT J DREss Ros. A

TABLE OUT sLIDE coMR /L0AD TABLE INDEX OUT 6 uNL0AD AFTER TIME TABLE INDEX ouT .22m GAGE RELEASE D FINE FEED I I, RATE N0.2 E OUT AFTER T/ME STOP RErRAcTIoN REAR E ROUGH lNTERMED/ATE GAGE SPARKOUT 2 nd RETRAcTloN REAR FINAL GAGE BACKOFF RESET 1 TO ZERO, R57: GAGE FIG. 8

Patented Nov. 27, 1973 3,774,349

8 Sheets-Sheet 5 FIG. 6

Patented Nov. 27, 1973 8 Sheets-Sheet 6 8 Sheets-Sheet Patented Nov. 27, 1973 Patented Nov. 27, 1973 8 Sheets-Sh a FIG.' /0

GRINDING MACHINE BACKGROUND OF THE INVENTION One method of grinding that has become very popular is that of grinding by the so-called controlled force method. One of the advantages of this method of grinding is that extremely high grinding forces can be used without danger of the abrasive wheel. The availability of such high forces in grinding has, however, led to another problem. That problem is that during the grinding of small bores, a limitation on the grinding force that can be used is present because of the limitation on the size of the spindle on which the abrasive wheel is mounted. Naturally, the wheel and spindle cannot be larger than the bore to be ground and, as a practical matter, must be considerably smaller due to the fact that it is desirable to leave a space between the It is, therefore, an outstanding object of the inventionto provide a grinding machine in which high force grinding can be used with small bores.

Another object of this invention is the provision of a grinding machine in which the spindle on which the abrasive wheel is mounted approaches the size of the bore being ground and can be tapered larger toward wheelhead for better stiffness.

A further object of the present invention is the provision of a grinding machine intended to use with a conical abrasive wheel having a long generatrix in which one part of the wheel is used for rough grinding and another part for finish grinding.

It is another object of the instant invention to provide a grinding machine to be used with an elongated abrasive wheel which is substantially longer than the bore to be ground and in which provision is made for causing the wheel to reside in the bore at two longitudinallyseparated positions, one for rough grinding and one for finish grinding with provision being made for introducing a gage into the workpiece during finish grinding.

A still further object of the invention is the provision of a grinding machine capable of operation with an elongated abrasive wheel, such that finish grinding may be performed with a freshly-dressed portion of the wheel without removal of the wheel for dressing during a given grinding cycle.

It is a further object of the invention to provide a grinding machine particularly adapted for use in a grinding cycle wherein dressing takes place during loading, wherein the workpiece is presented with an inprocess g age during the finish grind and wherein the grinding process does not have to be interupted between roughing and finish grinding to dress the wheel.

It is still a further object of the present invention to provide a grinding machine capable of grinding small bores more rapidly and with greater accuracy than in previously-known machines.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

SUMMARY OF THE INVENTION In general, this invention has to do with a grinding machine for generating a surface of revolution on a workpiece by the abrasive process. It has a base, a workhead mounted on the base for supporting and rotating the workpiece about the axis of revolution, and a wheelhead mounted on the base with a rotatable cantilevered spindle carrying an abrasive wheel at its outer end. The wheel is shaped with a frusto-conical surface with the small end located at the outer end of the spindle. The wheelhead is arranged so that the axis of the spindle lies at a substantial angle to the axis of the surface so that the generatrix of the surface of thewheel closest to the workpiece surface is parallel to the axis of the surface.

Means is provided for bringing about relative movement between the workhead and the wheelhead to bring about a grinding cycle, the relative movement consisting of movements perpendicular and parallel to the said'surface of revolution. A means is provided serving to bring about movement parallel to the axis from a first position, wherein the large portion of the wheel lies within the workpiece,'to a second position wherein the small portion of the wheel lies within the workpiece. A gage is provided which is introduced into the space between the surface of revolution and the wheel when the wheel is in the said second position.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a perspective view of a grinding machine embodying the principles of the present invention,

FIG. 2 is a perspective view somewhat schematic in nature of important portions of the machine,

FIG. 3 isa plan view of a portionof the machine taken on the line IIIIII of FIG. 2,

FIG. 4 is a plan view of a portion of the machine,

FIG. 5 is a vertical sectional view of the apparatus taken on the line VV of FIG. 4,

FIG. 6 is an enlarged plan view of a portion of the apparatus shown in FIG. 3,

FIG. 7 is an end elevational view of the apparatus shown in FIG. 6 taken on the line VII-VII of FIG. 6,

FIG. 8 is a cycle diagram showing the grinding cycle used with the grinding machine,

FIG. 9 is a sectional view taken on the line IXIX of FIG. 3 and,

FIG. 10 is a plan view of the portion of the machine shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, which best shows the general features of the invention, the grinding machine, indicated generally by the reference numeral 10, is indicated as being of the type shown and described in the patent of Uhtenwoldt et al., U.S. Pat. No. 3,593,463 which issued on July 20, 1971. It is provided with a base I 1 adapted to rest on a machine shop floor and on which the other elements of the machine are mounted. Extending around the base is an apron 12 to protect the operator from spray and the like. Overlying the apron is a cover 13 having a window 14 through which can be seen operative elements of the machine. Exposed above the apron is a wheelhead motor 15. Extending upwardly from the base rearwardly of that motor is a control box 16.

Referring now to FIG. 2, it can be seen that mounted on the base 11 under the cover 13 is a workhead table 17 arranged for sliding motion transversely of the base and a wheelhead table 18 arranged for motion longitudinally of the base. On the workhead table 17 is mounted a workhead 19 having a rotary spindle driven by a motor 21. Mounted in the workhead 19 and contacting the spindle is a workpiece 22. The transverse feed motion of the table 17 is provided by a cylinder 23 receiving hydraulic fluid from a valve 24, the hydraulic pressure originating in a power unit 25.

Mounted on the wheelhead table 18 is a wheelhead 26 driven by the motor 15 and having a spindle 27 carrying at its outer end an abrasive wheel 28. An hydraulic cylinder (not shown) provides for longitudinal movement of the table 18, while an oscillator 29 pro vides for short reciprocations of the wheel 28 in the workpiece while grinding.

FIG. 3 shows the arrangement of the table 18 and its relationship to the table 17. Overlying the upper horizontal surface of the table 18 is a secondary table 31 on which is mounted the wheelhead 26. Overlying the table 31 is a motor mount table 32 on which is mounted the motor 15 and which is normally fastened tightly to the table 31. It is used for adjustments of the motor 15. The underside of the ,table 31 is provided with a longitudinal groove 33 inwhich lies a bar 34. At the end adjacent the table 17, the bar 34 is provided with a vertical pivot 35 extending vertically into the table 18 while the other end of the bar 34 extends over the end of the table 18 and is provided with a block 36.

Referring now to FIG. 4, it can be seen that the abrasive wheel 28 is tapered, that is to say, it has the shape of a frustrum of a cone with the small end outboard of the spindle 27. One of its generatrices is at least twice as long as the axial length of the surface to be finished. In the illustrative example, the workpiece 22 is shown as the inner race of a ball bearing and the surface to be finished is the internal bore 37, which is a circular cylinder. It is shown as being ground by the centerless method, that is to say, it is supported on its outer surface on a hardened metal shoe 38. It is driven by a rotary platen 39 which is part of the wheel-head spindle and which engages one radial end surface. It is pressed against that platen by a clamp 41 which engages the other end radial surface of the workpiece. Extending through a suitable passage in the workhead 19 is an inprocess gage 42, which will be described more fully hereinafter. Mounted on the workhead table 17 and movable from an inoperative to an operative position is a dressing apparatus 43. A chute 44 is also mounted on the workhead for introducing workpiece 22 one at a time and for discharging them.

In FIG. it can be seen that the gage 42 is provided with a pair of fingers 45 and 46 which engage diametrically-opposite positions of the bore 37 and generate a voltage proportional to the size of the bore. Since this view is a vertical sectional view, the inclination of the axis of the spindle 27 to the axis of the bore 37 cannot be seen. However, the drawing illustrates very well the manner in which, when the small end of the abrasive wheel 28 is operating on the bore 37 considerable space is available for the introduction of the gage.

In FIGS. 6 and 7 are shown the details of the manner in which the table 31 carrying the wheelhead 26 and the motor is swiveled relative to the wheelhead table 18 to cause a generatrix of the abrasive wheel 28 to be parallel to the axis of the workpiece 22. The part of the bar 34 which emerges from the groove 33 on the underside of the table 31 the. bar is provided with a lock screw 47 which can be located in a screw hole 60 when the table 18 and the bar 34 have been swivelled 5. Mounted on the upper surface of the table 18 are two stop blocks 48 and 49 having threaded stops 51 and 52, respectively, extending therethrough. These stops engage the block 36 at either end of its swinging motion as the bar 34 pivots around the pivot 35. Bolted to the end surface of the table 18 is a circular cam segment 53 over the curved surface of which is stretched a chain 54 in the form of a roller chain engaged by a sprocket wheel 55 mounted at the lower end of a shaft 56. This shaft is rotatably mounted in the block 36 and has at its upper end an operating head 51a in the shape of a hexagonal element for operation by a wrench. Adjustment of the table 31 can take place by means of a threaded screw 57 rotatably mounted in the block 36 and operated by means of a wheel 58.

The operation of the invention will now be readily understood in view of the above description. The wheelhead motor 15 and the workhead motor 21 are energized, the hydraulic power unit 25 is set in operation, and the oscillator 29 and the grinding cycle are started in the usual way. A workpiece 22 is inserted into the work area from the chute 44 and comes to rest on the shoe 38. It is rotated about the axis of the surface 37 which is to be finished by means of' the platen 39 and the clamp 41. The surface of the bore 37 is first ground with the large portion of the wheel, there being sufficient space left in the passage through the workhead to receive the small end of the wheel at that time. The gage 42 is retracted and is out of the way of the wheel. When the rough grind is finished, the wheel is retracted to the right (in FIG. 5) and the small end of the abrasive wheel is brought into contact with the surface of the bore 37 for the finish grinding operation. At that time, the gage 42 is introduced into the bore 37 to keep a continuous indication of bore size.

FIG. 8 shows a typical grinding cycle that may be used with the present machine. At the point A, with the workpiece in position in the machine, the dressing apparatus 43 is moved into its operative position and the table 18 is moved to the left (as shown in FIG. 4) to cause the wheel 28 to pass over the diamond, which is the operative portion of the dressing apparatus. In other words, as the wheel moves to the left for insertion into the bore 37 in the workpiece, it passes over the dressing apparatus and its surface is renewed. Suitable compensation is, of course, made after the dress, but this is not part of the present invention. The abrasive wheel leaves the dressing apparatus at the point B and continues to the left until it reaches the point C. At that time, the abrasive wheel resides in the bore 37 with the large end coextensive with the bore and transverse feeding takes place in the usual way to produce a rough grind. After the rough grind has proceeded for a suitable period of time, the workhead table 17 is moved to the rear to retract the wheel from the working surface at the point D. Sparkout takes place to the point E. After the conventional motions of the table in the transverse direction, the point F is reached. The table 18 is then moved longitudinally to the point G so that the abrasive wheel 28 has its smaller end coextensive with the bore 37 of the workpiece. At that time, the finish grind is begun with a fine feed and the gage 42 is introduced into the bore. The gage determines the end of the finish grind at the point H. There is a retraction and a final fine feed to the point I, at which time the gage indicates the fact that the final size has been reached. The wheel is retracted away from the surface to point .l and the table is moved longitudinally to the right to the original retracted position at A, at which time the dressing compensation is made. Some of the details of the apparatus for bringing about the cycle are not shown in detail, because they constitute apparatus which is shown and described elsewhere. For instance, the gage inserting mechanism is shown in the patent application of Deranian et al., Ser. No. 879,695, filed Nov. 25, 1969 and now US. Pat. No. 3,634,980 dated Jan. 18, 1972. The apparatus which is used to move the table 18 to the two positions so that the different portions of the abrasive wheel 28 are co-extensive with the bore is shown in detail in FIGS. 3, 9, and of the drawings. On the base 1 1 is mounted a shelf 61 carrying a motor 62 whose vertically extending shaft 63 carries an eccentric 64. The eccentric engages a bridge 65 on a slide 66 slidably carried on the shelf. Mounted on this slide is a cylinder 67 whose piston 68 has a longitudinal rod 69. The other end of the rod is provided with a piston 70 which slides in a cylinder 71 carried on the underside of the table 18. This arrangement allows the table 18 to oscillate in either of the two wheel positions. The throw of the eccentric 64 is adjustable to permit the length of the oscillations to be changed. The cylinder 67 and the piston 68 regulate the small longitudinal movement of the abrasive wheel 28 within the workpiece, while the cylinder 71 and the piston 70 provide the large movement to remove the abrasive wheel from the work area for dressing and loading. A description of the chute 44 and the mechanism for introducing and releasing workpieces is shown in the patent of Hohler et al. US. Pat. No. 3,570,194 which issued Mar. 16, 1971.

It can be seen, then, that the present invention brings about a number of distinct advantages in grinding. This is particularly true where the workpiece is small and where, because of the fact that the spindle cannot be larger than the wheel, the spindle is limited in diameter. It is, of course, desirable to maintain the length of the spindle as small as possible to reduce its flexibility, but with the present invention, the spindle can be almost as large as the large portion of the frustrum of the cone in which the abrasive wheel is formed. Furthermore, the rough grind is performed at a point closer to the wheelhead bearings, so that the effective length of the spindle is less and its flexibility is less. During the finish grind, it is not desirable to use high force during grinding, so that the fact that the spindle is slightly longer at that time, presents no problem. Furthermore, since gaging is most important during the finish portion of the cycle, the present machine is set up so that gaging takes place only during the finishing and, yet, at that time, the small portion of the cone resides in the bore and sufficient space is available for an effective gage to be inserted without danger of interference between the wheel and the gage.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent l. A grinding machine for generating a surface of revolution on a workpiece by the abrasive process, comprising a. a base,

b. a workhead mounted on the base for supporting and rotating the workpiece about the axis of the surface of revolution,

c. a wheelhead mounted on the base and having a rotatable spindle carrying an abrasive wheel at its outer end, the wheel being shaped with a frustoconical surface with the small end located at the outward end of the spindle, the wheelhead being arranged so that the axis of the spindle lies at a substantial angle to the axis of the surface and so that the generatrix of the surface of the wheel closest to the workpiece surface is parallel to the axis of the workpiece surface,

d. means bringing about relative movements between the workhead and the wheelhead to bring about a grinding cycle, the relative movements consisting of movements perpendicular and parallel to the said axis of the surface of revolution, the means serving to bring about movement parallel to the axis from a first position wherein the large portion of the wheel lies within the workpiece to a second position wherein the small portion of the wheel lies within the workpiece, and

. a gage which is introduced into the space between the surface of revolution and the wheel when the wheel is in the said second position. v

2. A grinding machine'as recited in claim 1, wherein the gage is mounted on the workhead and is reciprocable relative thereto from an inoperative position to a position within the workpiece.

3. A grinding machine as recited in claim 1, wherein the workhead is mounted on a table which in turn is slidable' on ways for movement over the base in a direction perpendicular to the axis of the surface and wherein the wheelhead is mounted on a table which in turn is mounted on ways for movement parallel to the said axis.

4. A grinding machine as recited in claim 1, wherein a dressing apparatus is provided that is operative to dress the surface of the wheel during the loading of the grinding cycle.

5. A grinding machine as recited in claim 1, wherein the gage consists of two thin fingers whose ends engage diametrically opposite portions of the workpiece surface and who generate an electrical signal proportional to the diameter of the workpiece surface.

6. A grinding machine as recited in claim 5, wherein a switch is associated with the said means to initiate the movement of the wheel from the first to the second position when the surface of revolution reaches a predetermined size.

7. A grinding machine as recited in claim 6, wherein a hydraulic cylinder is provided to bring about the movement of the wheelhead from the first to the second position and a valve controls the motion of this hydraulic cylinder and is under the control of the said switch. 

1. A grinding machine for generating a surface of revolution on a workpiece by the abrasive process, comprising a. a base, b. a workhead mounted on the base for supporting and rotating the workpiece about the axis of the surface of revolution, c. a wheelhead mounted on the base and having a rotatable spindle carrying an abrasive wheel at its outer end, the wheel being shaped with a frusto-conical surface with the small end located at the outward end of the spindle, the wheelhead being arranged so that the axis of the spindle lies at a substantial angle to the axis of the surface and so that the generatrix of the surface of the wheel closest to the workpiece surface is parallel to the axis of the workpiece surface, d. means bringing about relative movements between the workhead and the wheelhead to bring about a grinding cycle, the relative movements consisting of movements perpendicular and parallel to the said axis of the surface of revolution, the means serving to bring about movement parallel to the axis from a first position wherein the large portion of the wheel lies within the workpiece to a second position wherein the small portion of the wheel lies within the workpiece, and e. a gage which is introduced into the space between the surface of revolution and the wheel when the wheel is in the said second position.
 2. A grinding machine as recited in claim 1, wherein the gage is mounted on the workhead and is reciprocable relative thereto from an inoperative position to a position within the workpiece.
 3. A grinding machine as recited in claIm 1, wherein the workhead is mounted on a table which in turn is slidable on ways for movement over the base in a direction perpendicular to the axis of the surface and wherein the wheelhead is mounted on a table which in turn is mounted on ways for movement parallel to the said axis.
 4. A grinding machine as recited in claim 1, wherein a dressing apparatus is provided that is operative to dress the surface of the wheel during the loading of the grinding cycle.
 5. A grinding machine as recited in claim 1, wherein the gage consists of two thin fingers whose ends engage diametrically opposite portions of the workpiece surface and who generate an electrical signal proportional to the diameter of the workpiece surface.
 6. A grinding machine as recited in claim 5, wherein a switch is associated with the said means to initiate the movement of the wheel from the first to the second position when the surface of revolution reaches a pre-determined size.
 7. A grinding machine as recited in claim 6, wherein a hydraulic cylinder is provided to bring about the movement of the wheelhead from the first to the second position and a valve controls the motion of this hydraulic cylinder and is under the control of the said switch. 